Atmospheric Remote Sensing: Instruments

Tunable Optical Profiler for Aerosol and oZone (TOPAZ) lidar

TOPAZ lidar instrument
TOPAZ operating from box truck during the CABOTS field study. Photo: Andy Langford, NOAA

The Tunable Optical Profiler for Aerosol and oZone lidar (TOPAZ) lidar was designed and built in 2006 at the NOAA Chemical Sciences Laboratory. TOPAZ incorporates state-of-the-art technologies to make it compact and lightweight as well as having low power consumption. These features have allowed for flexibility in its application to numerous air quality field studies, both airborne and ground-based. Its wavelength flexibility permits optimization for differing atmospheric conditions including interference from other atmospheric components and allows dual-DIAL operation – introduction to Differential Absorption Lidar (DIAL) techniques.

TOPAZ was originally configured and deployed on the NOAA Twin Otter aircraft to participate in air quality studies where it provided wide-area mapping of ozone and aerosol distributions and transport near urban sources. The first example of this application was the Texas Air Quality Study (TexAQS) 2006. As the lidar was flown over and around the Houston area collecting ozone and aerosol backscatter profiles from flight level to near ground level, it produced a three-dimensional picture of the distribution of ozone and aerosols in the study area. Additional information obtained from the lidar data included boundary height determination and ozone plume flux measurements.

After several years of airborne operation, TOPAZ was reconfigured for deployment in a box truck (and, more recently, a trailer) for ground-based operation. The addition of a two-axis (one automated) scanner permits data collection from a few meters above ground level (AGL) through 6-8 km AGL, dependent on atmospheric conditions. Recent examples of TOPAZ applications in this arrangement include the California Baseline Ozone Transport Study (CABOTS) 2016 and the Fires, Asian, and Stratospheric Transport - Las Vegas Ozone Study (FAST-LVOS) 2017 experiments.

TOPAZ is also part of the NASA Tropospheric Ozone Lidar Network (TOLNet) for ground-based profiling of tropospheric ozone. In addition to the occasional deployment to field experiments, TOPAZ makes routine measurements in support of TOLNET goals including satellite ozone measurement validation and creating a long-term ozone measurement record under varied atmospheric conditions on the Front Range of Colorado.

Basic Parameters Measured

  • Ozone concentration profiles
  • Aerosol backscatter profiles
TOPAZ example data
Time-height profiles of ozone concentrations and aerosol backscatter during the CABOTS experiment.

Typical Specifications

OutputNear-real-time ozone and aerosol profiles uploaded to NOAA CSL website
Tuning range285-310 nm (three wavelengths)
Pulse energy0.04 - 0.06 mJ/pulse
Pulse rate1 kHz with pulse-to-pulse tuning capability (333 Hz for each individual wavelength)
LaserDiode-pumped Nd:YLF laser quadrupled in LBO (intracavity) and CLBO (external) to 262 nm to pump Ce:LiCAF in a tunable cavity
Receiver0.5 m Newtonian telescope with two-axis (one automated) scanner
DigitizerHybrid analog-to-digital and photon counting transient recorder modules (16 bits, 20 MHz A/D sample rate, 250 MHz count rate)
Maximum profile altitude6 - 8 km above ground level (AGL)
Minimum profile altitude≤ 5 m AGL (minimum height limited by safety and/or terrain)
Eye-safe range150 m
Trailer dimensions32' L x 8.5' W x 11' H
Trailer shore power120/240 VAC 100 A service
Ozone profile vertical resolution5 m near surface to 1000 m at 8 km AGL
Ozone concentration accuracy≤ 2 ppbv
Ozone concentration precision3-10 ppbv (increasing with altitude and dependent on ozone and aerosol concentrations)
Auxiliary equipmentIn situ ozone sampling (2B instrument), Weather station
TOPAZ CAD rendering
CAD rendering (top) and schematic diagram (bottom) of TOPAZ and scanner in trailer-based installation.
TOPAZ schematic

Field Projects

Project NameDateLocation
AMMBECAirborne Methane Mass Balance Emissions in Colorado202407July 2024Colorado Front Range (ground site)
CUPiDS 2023Coastal Urban Plume Dynamics Study202007Summer 2023Guilford, Connecticut (ground site)
COVID-AQS 2020COVID Air Quality Study202003Spring 2020Boulder, Colorado (ground site)
FAST-LVOS 2017Fires, Asian, and Stratospheric Transport - Las Vegas Ozone Study201705May - June 2017Las Vegas, Nevada (ground site)
SCOOP 2016Southern California Ozone Observation Project201608August 2016southern California (ground site)
CABOTS 2016California Baseline Ozone Transport Study201605June - August 2016Visalia, California (ground site)
DISCOVER-AQ 2014Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality 2014201407July - August 2014Erie, Colorado (ground site)
DISCOVER-AQ 2013Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality 2013201309September 2013Houston, Texas (ground site)
LVOS 2013Las Vegas Ozone Study201305May - June 2013Angel Peak, Nevada (ground site)
UBWOS 2013Uintah Basin Winter Ozone Study 2013201301January - February 2013Horsepool, Utah (ground site)
UBWOS 2012Uintah Basin Winter Ozone Study 2012201202February 2012Horsepool, Utah (ground site)
CalNex 2010California Research at the Nexus of Air Quality and Climate Change201005May - July 2010Southern California (Twin Otter, aircraft based)
FRAQS 2008Front Range Air Quality Study200807July - August 2008Colorado Front Range (Twin Otter, aircraft based)
TexAQS 2006Texas Air Quality Study 2006200608August - September 2006Houston, Texas (Twin Otter, aircraft based)